218 
LOWER OOLITIC ROCKS OT ENGLAND: 
Limestone, and the absence here and there of beds that can be 
classed with the Lower Estuarine strata, indicate some local 
unconformity.* 
Sixteen feet of ironstone has in places been exposed in the 
workings of the Mid-Lincolnshire Iron Company. Mr. W. H. 
Dalton remarks that the rock is partly blue or green-hearted, and 
the lower portion of it is so crowded with phosphatic nodules as to 
be worthless for smelting. At the same time its hardness has 
deterred the makers of phosphatic manures from attempting to 
utilize it as a source of phosphoric acid.f 
The ironstone is extensively worked to a depth of 10 feet in 
pits on the west side of Greetwell : here, as elsewhere, the rock 
is mainly brown, and the greenish cores are rejected. On the 
eastern side of the valley the ore is obtained by means of tunnels 
driven into the hill-side beneath the Lincolnshire Limestone. I 
observed no indications there of the pebbly layer in the limestone 
above the ironstone. 
The details of the limestone-series differ a little from those in 
the pit just described. A thin layer of clay (3 or 4 inches) (5) 
separates the Walling Bed (4) from the Silver Beds (6) above, 
and the Silver Beds contain small pea-like pebbles of oolite. The 
beds on top comprise marly limestone and marls (7), and occa- 
sional layers of compact limestone (H) with scattered oolite grains 
and numerous small Gasteropods, as in the top beds of the Dean 
and Chapter pit, north of Lincoln. I obtained Natica cincta, 
Ceromya concentrica, and Acrosaltnia from the Lincolnshire. 
Limestone at this quarry. 
Inferior Oolite was proved to a depth of 65 feet on the hill 
north of the railway-cutting at Greetwell. J 
The Dean and Chapter pit is situated on the east side of the 
main road, about one mile north of the North Gate, Lincoln. 
Here the stone is quarried for building-purposes and to be burnt 
for lime. The section was as follows : 
Lincolnshire 
Limestone. 
8. 
7. 
fHard grey limestones, slightly 
oolitic, and much shattered 
j Marly layer with Pholadomya 
Irregular beds of shelly oolitic lime- 
stone (blue towards base), with 
oolitic marly and ferruginous 
layers ; small Gasteropods 
Blue shelly clay 
Buff, grey, and blue, compact and 
argillaceous limestones, with oc- 
casional oolitic and iron-shot 
grains ; bed with Pinna near the 
middle. These beds to a certain 
extent resemble the Kirton Beds : 
they yield no good building- 
stone - 
FT. IN. 
6 
* See also Ussher, Geology of Lincoln, p. 55. 
f Ussher, Geol. Lincoln, p. 39. 
j Geology of Lincoln, p. 55. 
This pit is also described in the Geology of Lincoln, pp. 53, 57. 
